Loss of function mutations in STK11, encoding the Ser/Thr protein kinase, LKB1 are responsible for the familial hamartoma syndrome, Peutz Jeghers Syndrome (PJS). Importantly, recent studies have revealed sporatic mutations in STK11 in a variety of human cancers, including lung adenocarcinomas. LKB1 phosphorylates and activates AMP dependent protein kinase in response to energy stress and thus plays a key role in energy homeostasis. The hypothesis guiding this proposal is that the LKB1-AMPK signaling axis evolved to limit cell growth under conditions of energy stress and that genetic or epigenetic aberrations, as well as transcriptional and post-transcriptional events that suppress LKBI function, allow tumor cells to override metabolic control mechanisms that normally limit cell growth under energy stress. The overall goal ofthe proposal is to elucidate the signaling and metabolic network controlled by LKB,1-AMPK and use this information to identify targets for therapeutic intervention in tumors that lack LKB1. The specific aims are: 1) to utilize technologies developed during the previous granting period to identify druggable downstream targets in the LKB1/AMPK signaling network; 2) to utilize mass spec metabolomics to identify metabolic pathways that are altered in cancers that result from loss of LKB1 and, 3) to use genetically engineered mice that develop cancers due to loss of LKBI, in the context of other genetic aberrationslobserved in human lung cancers, to evaluate drugs or drug combinations, predicted on the basis of in vitro studies in Aims 1 and 2.